1. Field
This disclosure relates to call control processing, more particularly to call control processing distributed across multiple network devices in multimedia communication system.
2. Background
Multimedia communications systems typically involve using a data network of a standardized format to provide audio communications, such as Voice over Internet Protocol (VoIP), and/or audiovisual communications such as videoconferences. In the example of VoIP, the standardized format is Internet Protocol. Other types of standardized data networks may exist, including Frame Relay (FR) or Asynchronous Transfer Mode (ATM) as well as hybrids of any of the above, as examples.
These data networks typically require some equipment that allows the data being carried in the standardized format to be converted into a data stream compatible with telephone networks. For example, a user may have a VoIP phone as the data network terminal within a corporation at campus A. The user may want to call a party at campus B. The party at campus B may have a VoIP phone as well, but the two corporate campuses are connected by the public switched telephone network (PSTN). Alternatively, the party at campus B may be using a PSTN phone. In either case, the VoIP call must be converted into a format that allows it to be carried across the PSTN. Note that as used here, PSTN will include Integrated Services Digital Networks (ISDN).
The converters are usually a particular type of network device referred to as a gateway. The gateway receives a call from the PSTN bound for a data network terminal or from the data network terminal bound for the PSTN. The gateway converts the incoming format into the outgoing format. The handling of each call, either inbound or outbound, is handled within the gateway. These architectures allow processing to be distributed across more than one processor, providing a high capability at the gateway.
The distribution of processing tasks generally does not include call control. Call control determines how each call is handled. Currently, most gateways have a single CPU that handles call control, meaning that as each call comes into the gateway a single CPU translates the call control data and determines which processor will handle that call. This is repeated for every packet or other set of data that enters the gateway for conversion. Having a single CPU for handling call control gives rise to the possibility of a single point of failure in a network device, as well as not capitalizing upon the presence of any other processors that may be in the system.